Mercury contamination is a serious environmental concern usually associated with aquatic food webs. We tested for the presence of mercury in winged queens and males of four ant species and found that invasive red imported fire ants (Solenopsis invicta) contain high levels of mercury typical of aquatic insects. Mercury concentrations in male fire ants were 51 % higher than those in females and 89–199 % higher than those in other ant species from the same location. Fire ant sexuals fly long distances on their mating flights and are a major food source for arthropod and vertebrate predators and may thus transfer mercury through food webs.